DEVICE IN IMPACT MACHINES

DISPOSITIF FAISANT PARTIE D'UNE MACHINE A PERCUSSION

English Abstract

Device in impact machines. The device comprises a first chamber (5) which is
connected to an accmulator (6) and the pressure of which is used to hold
together a set of rods (2) forming part of the drill tool. Furthermore there
is a second chamber (7) to damp the recoil from the set of rods.

Claims

3
Claims:
1. Device in impact machines for drilling by means of a drill string
comprising a set of tubes (1) for transferring rotation to a drill bit and a
set of rods (2) arranged centrally in the set of tubes for transferring
impact energy from a hammer piston (4) movable to-and-fro in a machine
housing (3) to said drill bit, characterized in that said
machine housing (3) comprises a first chamber (5) connected to an
accumulator (6), a second chamber (7) and a piston (8), whereby said piston
transfers a force determined by the liquid pressure in said first chamber to
said set of rods (2) and is movable into said second chamber with close fit
to entrap a liquid volume damping the recoil from said set of rods.
2. Device according to claim 1, characterized in that a
check valve (9) is arranged between said first (5) and second (7) chambers
and that the check valve is directed such that it allows liquid flow from
said first chamber to said second chamber.

Description

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1
Device in impact machines
The present invention relates to a device in impact machines for drilling,
preferably in rock, by means of a drill string comprising a set of tubes and
a set of rods arranged in the set of tubes.
When drilling with drill strings of the above mentioned kind the problem
arises that the rods forming part of the set of rods not always abut against
each other when the hammer piston hits the rearmost part of the set of rods.
This results therein that the energy of the harnmer piston only partly is
transferred to the drill bit at the other end of the drill string.
The present invention, which is defined in the subsequent claims, aims at
achieving a device of the kind mentioned above where the rods forming part
of the set of rods abut against each other when the hammer piston hits. The
invention furthermore aims at achieving an efficient damping of the recoil
without jeopardizing the abutment between the rods of the set of rods. This
problem is substantially larger with this type of drill string than with a
drill string where the rods are connected with each other since the energy
of the recoil from the rock substantially entirely is transferred to the
rearmost part in the set of rods. This part, therefore, obtains a large
kinetic energy and will thus move far. If this occurs it will take a long
time before the rods in the set of rods abut against each other again. This
means that drilling can only occur with low frequency if the rods are to be
held against each other during the drilling. With the present invention it
is possible to hold the rods against each othex also at high frequencies.
An embodiment of the invention is described below with reference to the
accompanying drawing which schematically shows a section through a device
according to the invention.
The device shown in the drawing comprises a machine housing 3 on which a
front part ll is secured. The drilling device comprises a drill string
comprising a set of tubes, in the drawing represented by the drill sleeve 1
which forms the rearmost part, and a set of rods 2, which in the drawing is
represented by an adapter 2 arranged in the machine: A not shown drill bit
is arranged at the front end of the drill string. The drill bit is rotated
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2
by means of the sec of tubes which in its turn is rotated by a rotary motor
12 via a toothed wheel 13 which gears with teeth 1<< on the drill sleeve 1. A
hammer piston 4 is movable to-and-fro in the machine housing 3 in the usual
way. The hammer piston transfers its energy to the adapter 2 in the set of
rods. This energy is then trans:Eerred from rod to rod in the set of rods and
from the set of rods to the drill bit. A sleeve 15 and a piston 8 axe
siidably arranged in the machine housing 3. These transfer to the adapter 2
a force determined by the pressure in a first chamber S. This pressure acts
on a forwardly directed surface 17. This force is used during drilling to
hold the rods of the set of rods together. Chamber S is connected to an
accumulator 6 which is supplied with pressure liquid from a pressure liquid
source 16. Piston 8 is with close fit movable into a second chamber 7. This
means that the recoil from the rock is efficiently damped because liquid is
pressed out through the narrow slot between piston 8 and the machine housing
3. In order to avoid cavitation when piston 8 moves out of Chamber 7 a CheC~C
valve 9 is arranged between the first and second chambers and directed such
that liquid flow is allowed from first chamber 5 to second chamber 7.
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Representative Drawing